Arf-GAP with GTPase, ANK repeat and PH domain-containing protein Pleckstrin homology (PH) domain. AGAP (also called centaurin gamma; PIKE/Phosphatidylinositol-3-kinase enhancer) reside mainly in the nucleus and are known to activate phosphoinositide 3-kinase, a key regulator of cell proliferation, motility and vesicular trafficking. There are 3 isoforms of AGAP (PIKE-A, PIKE-L, and PIKE-S) the longest of which PIKE-L consists of N-terminal proline rich domains (PRDs), followed by a GTPase domain, a split PH domain (PHN and PHC), an ArfGAP domain and two ankyrin repeats. PIKE-S terminates after the PHN domain and PIKE-A is missing the PRD region. Centaurin binds phosphatidlyinositol (3,4,5)P3. PH domains have diverse functions, but in general are involved in targeting proteins to the appropriate cellular location or in the interaction with a binding partner. They share little sequence conservation, but all have a common fold, which is electrostatically polarized. Less than 10% of PH domains bind phosphoinositide phosphates (PIPs) with high affinity and specificity. PH domains are distinguished from other PIP-binding domains by their specific high-affinity binding to PIPs with two vicinal phosphate groups: PtdIns(3,4)P2, PtdIns(4,5)P2 or PtdIns(3,4,5)P3 which results in targeting some PH domain proteins to the plasma membrane. A few display strong specificity in lipid binding. Any specificity is usually determined by loop regions or insertions in the N-terminus of the domain, which are not conserved across all PH domains. PH domains are found in cellular signaling proteins such as serine/threonine kinase, tyrosine kinases, regulators of G-proteins, endocytotic GTPases, adaptors, as well as cytoskeletal associated molecules and in lipid associated enzymes.